Operation of smoke detectors in dusty conditions

Owned by Vasily T.
Last updated: Oct 26, 2023 by Vladimir Tayzhev
3 min read

In the case of using a multitude of sensors in dusty rooms, it becomes necessary to distinguish fake sensor responses from true ones.

Let us connect the VT560 smoke detector, and rename it “Fire-1”.

Create a Fire ON trigger, with default fields. This is a trigger for temporarily storing the value of the smoke detector.

Create a Fire Alarm trigger, with default fields. The triggering of this trigger means a steady smoke signal.

Create Fire ON logic. This logic monitors the active state of the smoke detector (including the Fire ON trigger) and resets it by turning off the power. The power is turned off by applying a pulse to the Analog Power element, the default pulse duration is 15 seconds. You can change the pulse duration in the properties of the Analog Power element. Remember that this will disable all analog sensors connected to the unit. If the system has logic circuits that can be triggered when these sensors are turned off, they will go into the active state and perform the appropriate actions.

 

Create Logic - Fire OFF. This logic disables the Fire ON trigger if the smoke detector is in an inactive state (normal) for more than 20 seconds. This delay is needed to turn the sensor on after a power failure. Thus, these two logics ensure the stability of the value of the Fire ON trigger for false alarms. the trigger remains in the "alarm" state for a time, which is formed from the duration of the Analog Power pulse (the default is 15 seconds) and the delay to disable the trigger (that means 20 seconds). Also, this logic disables the trigger of a steady smoke signal - A fire Alarm. If you want to reset this trigger manually, or for some other conditions, remove this action from the logic diagram.

 

Create Fire Alarm Logic. This logic includes the Fire Alarm trigger, in the absence of a false signal (the Fire ON trigger is active for more than 1 minute). This logic also resets the smoke detector every minute to update its status. Time delay for the Fire Alarm trigger can be reduced, but in our case, it should be at least 40 seconds: 15 sec for the Analog Power reset pulse, 20 seconds to turn the sensor on, and 5 seconds to eliminate potential conflicts when logic circuits are triggered.

 

Now you can create logic that sends out alarm messages about the fire's response to a change in the Fire Alarm trigger state.